To facilitate the independent reading, interpretation, and critical evaluation of the documents collected in the body of this work, this Introduction provides an elementary overview of the events and issues of the Galileo affair, together with some of its historical background and a sketch of a philosophical approach to its study. By the “Galileo affair”¹ is meant the sequence of developments which began in 1613 and culminated with the trial and condemnation of Galileo Galilei by the Roman Catholic Inquisition in 1633. Galileo Galilei is the Italian scientist and philosopher whose contributions to astronomy, physics, and scientific instrumentation and methodology...

Thursday morning I had breakfast with our Lordships, and, when asked about school by the Grand Duke,¹ I gave him a detailed account of everything, and he seemed to be very satisfied. He asked me whether I had a telescope, and I told him Yes and so began to relate the observation of the Medicean planets² which I had made just the previous night. Then Her Most Serene Ladyship³ inquired about their position and began saying to herself that they had better be real and not deceptions of the instrument. So their Highnesses asked...

⟨351⟩ In order to remove (as much as the blessed God allows me) the occasion to deviate from the most correct judgment about the resolution of the pending controversy, I shall try to do away with two ideas. These are notions which I believe some are attempting to impress on the minds of those persons who are charged with the deliberations, and, if I am not mistaken, they are concepts far from the truth.

The first is that no one has any reason to fear that the outcome might be scandalous; for the earth’s stability and sun’s motion are so...

[1]² As Your Most Serene Highness knows very well, a few years ago I discovered in the heavens many particulars which had been invisible until our time.³ Because of their novelty, and because of some consequences deriving from them which contradict certain physical propositions⁴ commonly accepted in philosophical schools, they roused against me no small number of such professors, as if I had placed these things in heaven with my hands in order to confound nature and the sciences.⁵ These people seemed to forget that a multitude of truths contribute...

⟨377⟩ To the Most Illustrious and Most Reverend Lord Cardinal Orsini:¹

[1]² I am honored that Your Most Eminent and Most Reverend Lordship has asked me to put into writing what I explained to you orally ten days ago, and the honor is much greater than I and my insubstantial discussions deserve. My only means of reciprocating, at least in part, being prompt obedience, here I am ready to serve and obey you in accordance with your request. I shall try to do so in the briefest and most concise way possible for such an amazing problem as the investigation...

Besides the common duty of every good Christian, there is a limitless obligation that binds all Dominican friars, since they were designated by the Holy Father the black and white hounds of the Holy Office. This applies in particular to all theologians and preachers, and hence to me, lowest of all and most devoted to Your Most Illustrious Lordship. I have come across a letter⁴ that is passing through everybody’s hands here, originating among those known as “Galileists,” who, following the views of Copernicus, affirm that the earth moves and the heavens stand still....

⟨509⟩ To the Very Illustrious and Very Distinguished Mr. Francesco Ingoli of Ravenna:

[1]¹ Eight years have already passed, Mr. Ingoli, since while in Rome I received from you an essay written almost in the form of a letter addressed to me.² In it you tried to demonstrate the falsity of the Copernican hypothesis, concerning which there was much turmoil at that time. In particular, you dealt with the location and motion of the sun and the earth, maintaining that the latter is at the center of the universe and completely motionless and the former in motion and as far...

I am still afflicted with the same ills which Your Most Serene Highness found me to have when I was very undeservedly favored and honored by your infinite kindness. To my suffering from the corporal afflictions has been added a more painful mental one, namely not to have been able nor to be able still (at least in part) to satisfy the suggestions of Your Highness, by putting together in accordance with my inclination some discussions on problems that I think would not displease you. Thus I am forced to implore you very...

… I have not been able yet to see the Master of the Sacred Palace in regard to the question of Mr. Galilei. However, because I hear that there has been set up a Commission of persons versed in this profession, all unfriendly to Galileo, responsible to the Lord Cardinal Barberini,² 1 have decided to speak about it to His Eminence himself at the earliest opportunity. Furthermore, because they are thinking of calling a mathematician from Pisa, named Mr. Chiaramonti³ and rather unfriendly to Mr. Galileo’s opinions, it will be necessary that His Highness have someone talk to him, to...

Summoned, there appeared personally in Rome at the palace of the Holy Office, in the usual quarters of the Reverend Father Commissary, fully in the presence of the Reverend Father Fra Vincenzo Maculano of Firenzuola, ⟨337⟩ Commissary General, and of his assistant Reverend Father Carlo Sinceri, Prosecutor of the Holy Office, etc.

Galileo, son of the late Vincenzio Galilei, Florentine, seventy years old, who, having taken a formal oath to tell the truth, was asked by the Fathers the following: